In certain automatic control systems, such as, mass and/or rapid transit operation, it is necessary to determine the direction of movement of the railway vehicle or train. When a train stops at a station, it is essential to prevent "roll-back" or "run-back" in order to preclude injury to boarding and discharging passengers. It will be appreciated that inadvertent rearward movement of the train can cause a commuter to be thrown down or to be tossed against the bulkhead, door jams or the like. In addition, "roll-back" can result in the misalignment of the doors of the vehicles and the gates on the station platform which could make it difficult, if not impossible, for passengers to board or alight from the train. Thus, in order to provide the highest degree of safety to users and operators of mass and/or rapid transit systems, it is highly desirous to detect the direction of movement of the vehicle or train so that corrective measures may be immediately taken to preclude the development of a dangerous situation.